Tiger: first impressions: installation

So I had a minor apoplectic fit last night. High off the almost laughable ease with which I had installed (upgrade, not clean install) Tiger on my slower Mac (a 667 MHz/512 MB RAM G4 TiBook), I did a cursory backup of the data on my faster machine (a dual 1.42 GHz/1.5 GB RAM G4 desktop) and set out to install the new OS. And that's when my troubles began:

The installation kept crapping out on the part where it verifies the destination volume (i.e. the hard drive) and telling me to try again. After about 3 tries and no successes, I got the brilliant idea to run Disk Utility to see if there were any problems with my main hard drive. Note that one of Disk Utility's most unfortunate shortcomings is that it can't verify or repair the disk it's running from; since I had booted off the installation DVD-ROM, I could run verification and repair processes on the main hard drive from the copy of Disk Utility located on the DVD-ROM. It turned out that there was a problem with the disk, but when I tried to repair it, the repair failed. So, now what?

With barely-restrained panic, I did some Googling, and came up with this article, which basically told me to reboot in single user mode and run the fsck utility, which is better at fixing problems, apparently, than the asr utility that Disk Utility uses to fix hard disks. So I did reboot into single user mode, and ran fsck -fy at the command prompt. Sure enough, it found problems, said it repaired them, and that the disk was now fixed. So then I rebooted and tried installation again: same problem. Huh?

OK, back to the drawing board. This article said that I needed to keep running fsck -fy from the single user prompt until it showed that no errors were found. So I did. 5 or 6 tries later, I still kept getting the message that errors were fixed, but not that no errors were found. Then I noticed that I kept seeing the same error whenever I ran fsck: "Overlapped extent allocation (file 2684056d)". So I did a Google search on "overlapped extent allocation", and hit the jackpot (search for "Manually fix Overlapped Extent Allocation Errors without Diskwarrior" on the page).

Apparently, fsck can't fix overlapped extent allocation errors (basically this is when two files seem to be sharing the same memory space); the only way to fix this error (well, the only way to fix this error without buying expensive disk repair software) is to remove the offending file (identified by the number in the error message above). This, as you might imagine, could be troublesome if the file in question is a system file. So, to find out the path of the file, I ran find / -inum 2684056 -print. Note that I changed the -inode attribute in the article to -inum; there is no -inode attribute for the find command. More details can be found by running man find at the command prompt.

Anyway, to my everlasting relief, it turned out that the file was an audio file in my iTunes library; I had actually caused the problem myself earlier that day by backing up my iTunes library (which is on an external firewire hard drive) to the main hard drive on my computer. So, again from the single user mode prompt, I mounted the hard drive (mount -uw /) and removed the troublemaking file. After rebooting, the installation went off without a hitch. Hallelujah!

All told, the installation was actually very smooth. More first impressions to come...